Influence of Zinc on Coarsening of delta-Ni2Si Particles, Aging Behavior and Hardness in a Cu-Ni-Si Alloy

摘要

In the present paper, the aging precipitation and coarsening of disk-like delta-Ni2Si particles in Cu and Cu-10Zn alloys aged at 450 degrees C have been investigated by hardness, electric resistivity measurement and transmission electron microscopy observation. The coarsening dynamics of the average diameter of the delta-Ni2Si particles coincides with the t(1/3) time law for both alloys. The coarsening of the diminution of supersaturation related to aging time t coincides with the t(-1/3) time rule. Adding Zn to the Cu-Ni-Si alloy increases the growth and coarsening rate of the particles mainly because of the increased diffusivity D of the delta-Ni2Si particles in the matrix. The value of D of the delta-Ni2Si particles in the Cu-xZn (x = 0, 10 wt.%) matrix and the Cu/delta-Ni2Si interfacial energy gamma are independently calculated by using the Lifshitz-Slyozov-Wagner theory which was extended to include disk-like particles by Boyd and Nicholson. The values of D and gamma increase from 0.77 x 10(-19) to 2.21 x 10(-19) m(2)/s and 0.19 to 0.63 J/m(2), respectively, when Zn is added to the Cu-Ni-Si alloy. These calculations and the analysis show that the properties of Cu-Ni-Si-Zn alloy can significantly be enhanced by reducing the aging temperature.